For an industry that many people won't admit they've ever patronized, pornography has had an amazing impact on virtually every new medium, from cave painting to photography. Dirty pictures have been credited with ensuring the future of the VCR, boosting cable TV subscriptions, helping to kill off the Betamax and HD DVD formats, and (perhaps most important) driving the growth of the Internet.

In fact, the adult entertainment industry has been on top of many of the Net's most crucial tech innovations--but not because it invented any of them.

According to Lewis Perdue, author of Eroticabiz: How Sex Shaped the Internet, "without business and technical pioneers in the online sex business, the World Wide Web would never have grown so big so quickly." (Not that we think size matters.)

The innovations happen because porn is "an ecosystem in which participants are willing--indeed forced--to experiment, and where experimentation isn't hobbled by common sense, good taste, or bureaucracy," says Bruce Arnold, principal of Caslon Analytics, a research and analysis firm from Braddon, Australia, that specializes in regulatory issues, demographics, social trends, and technologies.

In an industry notorious for erecting walls of secrecy, hard numbers are difficult to come by, and most evidence is anecdotal. Still, it's clear that the adult industry has helped shape the Internet as we know it today, even if it has also been at the forefront of a number of less savory innovations. Let's take a look at a not-entirely-dirty dozen.

1. Nice:Online Payment Systems

Photograph: Rachel Ashe/WikimediaThe next time you buy something at Amazon or another online retailer, marveling at the ease and security of e-commerce, don't just thank Jeff Bezos, thank Richard Gordon. In the mid-1990s Gordon founded Electronic Card Systems, which pioneered credit card transactions for a wide range of disreputable sites, according to the New York Times.

"While riches were being minted and squandered in the dot-com '90s, Gordon made a fortune by taking a commission for processing sales on a range of sites...like ClubLove, which published the Pamela Anderson-Tommy Lee sex tape," wrote the Times' Brad Stone. (Through his lawyer, Gordon officially denies having been involved with pornography, but Stone found more than a dozen current and former employees who suggested otherwise.)

According to Forrester Research, Web users spent about $1.3 billion on online porn in 1999. That represented about 8 percent of all Net commerce that year, and more money than people spent online on books or plane tickets. Back then, it was the Internet's leading industry. By 2006, however, Net porn was generating just $2.8 billion in revenues--a much smaller piece of the online pie, which had grown to $150 to $200 billion.

Richard Gordon also owns a Web design firm that created sites for the American Bible Society--or at least it did so until Stone contacted the ABS last May--proving that Gordon could swing both ways.

2.Naughty: Spam

Artwork: Chip TaylorThe sex industry didn't invent spam, but it provided ample proof of just how profitable a spam-driven business could be. In the late 1990s countless daily come-ons for porn sites were a fact of life for most people with an inbox. Between 2001 and 2002, adult-oriented spam rose by 450 percent, according to Cyber Atlas. By April 2003, one out of every five spam messages sent were for adult sites. However, by October 2008, that number had shrunk to a puny 2 percent, according to Symantec's State of Spam report [PDF], eclipsed by unsolicited offers for loans, pills, and other spam scams.

3. Nice: Streaming Content

Before CNN.com or YouTube started filling the Internet with streaming video, X-rated sites were pumping out videos of adult stars doing what comes naturally (or not), over and over and over.

In a May 2001 interview with NPR, Danni Ashe (pictured), founder of seminal softcore site Danni's Hard Drive, noted that "the adult entertainment industry was the first to use streaming JPEG push video, which was video that worked...in the browser and didn't require a plug-in. I think as an industry we tend to jump in a little bit faster and tweak the technology and try to get it to work faster."

In 2003, Acacia Research sued dozens of porn sites for allegedly violating its patents on streaming video. The patent portfolio company sued the pornsters in part because they were easy targets, but also because that's where most of the video action was. Subsequently Acacia got around to securing licenses from Disney, the New York Times, and other less titillating video streamers.

"Without programming pioneers trying to perfect video streaming software that would deliver images of copulation and procreation to paying customers hooked up with a 28.8kbps dial-up modem, it is unlikely that CNN would be effectively delivering news clips of global breaking news," wrote Lewis Perdue in Eroticabiz.